I’ve taken to walking in the early mornings when extreme heat makes it impossible to do otherwise. Walking clears my head. It’s how I root myself; it helps me, literally and metaphorically, keep my feet on the ground. On hot days, it also has gotten me thinking about Los Angeles above the surface of the streets.

I’m referring to shade, which I can’t help but map informally as I stroll. By the end of my walks, I am sweaty and heat-saturated, looking for whatever patches of cover I can find in my mid-city neighborhood.

I know: Sun colors the Southern California mythos. “Come to Los Angeles,” Danny DeVito’s character declares in the film “L.A. Confidential.” “The sun shines bright, the beaches are wide and inviting, and the orange groves stretch as far as the eye can see.” No one makes a legend out of shade.

That’s too bad, because when it gets hot, whatever takes the edge off is as essential as the sun. Think about it, how it feels to step outside after sunset, or into the morning haze of the marine layer. Just to imagine it makes me sigh with relief.

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There’s a reason the best film noirs take place at night, and it’s not only that they’re shot in black and white. Los Angeles flexes, loosens its shoulders, out from under the tyranny of the sun.

There’s a reason the best film noirs take place at night, and it’s not only that they’re shot in black and white.

But mostly the sun wins. Shade is sparse here, even in adequately planted communities. My street has a decent number of mature trees: sycamores mostly, with some cypresses, one excellent redwood and a smattering of palms. Just a few blocks over, though, a line of new redbuds doesn’t even reach my height.

And our urban forest is growing sparser. According to a study published last year by USC’s Spatial Sciences Institute, tree and shrub cover in Los Angeles County declined by an average of 1.2% annually between 2000 and 2009. In 2008, Greg McPherson of the U.S. Forest Service reported that 21% of Los Angeles had tree coverage. Nine years later, the MIT Senseable City Lab “Treepedia” found that number had dropped to just 15.2%.

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The causes are many: everything from “mansionization” — in which old houses are replaced by bigger ones extending to the edge of property setbacks — to tree disease, pests (especially the polyphagous shot hole borer, a beetle) and sidewalk repair.

Removing diseased trees, of course, or those that uproot sidewalks, is necessary — as long as they’re replaced. Too often, they aren’t, especially in less affluent neighborhoods.

The USC study found that Baldwin Park saw “a 55% loss of green cover on single-family residential lots — from 70% to 31% — in the mere span of nine years.” Downey, Compton and San Pedro lost 20% of their cover during the same span.

“People think of trees as decoration,” Deborah Bloome, senior director of policy and research for TreePeople, headquartered in Coldwater Canyon Park, told me recently, “but really, trees are part of the city’s infrastructure. And they appreciate over time.”

What Bloome means is that trees add to human resilience in these warming times.

That’s especially the case in Southern California. For all that we like to imagine the region as Edenic, the reality is often the opposite. Since July 6, temperatures in Los Angeles have topped 90 degrees 20 times. Wildfires in Riverside, Orange and San Diego counties have ravaged more than 40,000 acres.

The urban forest can reduce street level temperatures, through shade as well as water evaporation, by as much as 3.6 degrees.

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More to the point, planting and maintaining healthy trees offers a means to seize the warming future, to remake it on our terms. Do we have another choice? The U.S. Interior secretary blames “environmental terrorist groups,” not climate change, for the severity of California’s wildfires. The president is challenging the state on emissions standards for automobiles and rolling back clean air rules.

In 2006, then-Mayor Antonio Villaraigosa announced a Million Tree Initiative for Los Angeles. A good idea, but by the time he left office in 2013, fewer than half the promised trees were planted.

Now Mayor Eric Garcetti is developing another plan, OurLA2040, for growth over the next 20 years. In addition to more public transportation and affordable housing, expansion of the urban forest ought to be a centerpiece — and before 2040, please.

To look at the MIT Treepedia online map of Los Angeles is instructive. The basin is represented by a lattice of green and yellow-green lines interspersed with gaps and streaks of brown. What I see is faithful to what I see in my neighborhood: leafier streets north of Pico, less green along the sidewalks I frequent most.

I think about that one excellent redwood I pass by when I walk. It must account for some of the green near me. I was excited the first time I noticed it, as if an exotic visitor had moved in next door. These days, I’m just glad it’s still standing, so that as the heat rises, I can find refuge in its shade.

Overcoming opposition from companies making high-interest loans, the state Legislature was poised to give final approval Friday to a bill to cap interest rates on installment loans between $2,500 and $10,000.